1. Field of the Invention
The present invention relates to a chloroprene rubber, a method for producing the same, a chloroprene rubber composition and a vulcanized product thereof. More specifically, it relates to a chloroprene rubber for use in general industrial rubber products and processed goods such as automobile parts.
2. Description of the Related Art
Chloroprene rubbers, which are superior in heat resistance, weather resistance, ozone resistance, chemical resistance, and others, have been used in various fields including general industrial rubber products and automobile parts. Such molded chloroprene rubber articles are generally produced by molding a composition containing a chloroprene rubber, a vulcanizing agent, a vulcanization accelerator, a filler, and others into a particular shape and vulcanizing the molded article.
These chloroprene rubber compositions have a disadvantage that the rubber compositions are adhesive to rolls during roll processing, leading to deterioration in processability. Thus proposed as a method for reducing the adhesiveness to rolls was a means of blending 1 to 50 parts by mass of a chlorinated polyethylene to 100 parts by mass of a chloroprene rubber (see Patent Document 1).
The vulcanized product of the chloroprene rubber composition is also desired to be superior in physical properties such as tensile strength and tear strength. Thus proposed as a method for improving these physical properties was a means of blending 0.5 to 2.0 parts by mass of a fatty acid having a carbon number of 36 or more to 100 parts by mass of a chloroprene rubber (see Patent Document 2).
Also proposed as a method for reducing adhesiveness of the rubber composition to rolls and improving the physical properties of the vulcanized product was a means of producing a chloroprene rubber comprising polymerizing 2-chloro-1,3-butadiene: 80 to 99.7 parts by mass, sulfur: 0.3 to 2 parts by mass, and a monomer copolymerizable with 2-chloro-1,3-butadiene: 0 to 19.7 parts by mass at a polymerization temperature of 35 to 40° C., terminating the polymerization when the conversion rate reaches 70 to 90%, adding a thiuram compound, and peptizing the resulting mixture to a Mooney viscosity of 51 to 67 (see Patent Document 3).